Polymerizable composition for optical material, optical material, and method for producing optical material

ABSTRACT

A polymerizable composition for an optical material containing tolylene diisocyanate, an aliphatic polyisocyanate having 4 to 8 carbon atoms, one or more polythiols selected from pentaerythritol tetrakismercaptoacetate and pentaerythritol tetrakismercaptopropionate and an active hydrogen compound containing two or more active hydrogen groups, is provided.

The present application is a Continuation Application of U.S.application Ser. No. 12/850,275, filed Aug. 4, 2010, which claimspriority under 35 U.S.C. §119(e) to U.S. Provisional Patent Application61/231,404,filed Aug. 5, 2009 and claims foreign priority to JapaneseApplication No. 2009-182125, filed Aug. 5, 2009 and 2010-20677, filedFeb. 1, 2010, the entire contents of each of which are incorporated byreference herein.

BACKGROUND

1. Technical Field

The present invention relates to a polymerizable composition for anoptical material, and more particularly, to a polymerizable compositionfor an optical material containing a specific polyisocyanate and aspecific polythiol compound. The invention also relates to an opticalmaterial obtainable from this polymerizable composition for an opticalmaterial, and a method for producing this optical material.

2. Related Art

Plastic materials have been traditionally used as a substituent forinorganic materials in the application of optical parts. These plasticmaterials are lightweight and are not susceptible to breakage, and canbe tinted, as compared with the inorganic materials that have hithertobeen used. Therefore, plastic materials are being preferentially used.Particularly, plastic materials having high refractive index aredesirable for optical parts such as lenses, and suggested examples ofsuch plastic materials having high refractive index includesulfur-containing urethane (thiourethane) resins described in JapaneseUnexamined Patent Publication Nos. H02-153302 (1990-153302), H01-295202(1989-295202), H02-000802 (1990-000802), S63-046213 (1988-046213),S64-045611 (1989-045611).

SUMMARY

However, aromatic thiourethane resins for which practicalization hasbeen difficult in the conventional technologies from the viewpoint ofcolor, even though being materials having high refractive index, can nowbe used for practical purposes, as a result of development of additivessuch as a bluing agent. On the other hand, in recent years, it isdesirable to use plastic materials even in those optical parts used inapplications where high durability is demanded. Among such plasticmaterials, a material having less change in optical properties overtime, especially in color, that is, a material having high lightresistance, is demanded.

Meanwhile, many of plastic materials having high refractive indexexhibit low tinting property of the base material. Thus, those plasticmaterials are not satisfactory for applications of optical parts wherehigh tinting property is demanded, and an improvement of tintingproperty is now in demand. Furthermore, there have been demands forimprovements in refractive index and heat resistance; however, heatresistance and tinting property are in a trade-off relationship, suchthat, in general, when heat resistance increases, tinting property isdecreased.

The present inventors found that a material having a high refractiveindex and having both high heat resistance and high tinting property canbe obtained by using a polyisocyanate formed from a specific isocyanateand a specific polythiol compound in combination, thus completing theinvention.

Specifically, the invention includes the following.

(1) In one embodiment, there is provided polymerizable composition foran optical material, containing tolylene diisocyanate, an aliphaticpolyisocyanate having 4 to 8 carbon atoms, and one or more polythiolsselected from pentaerythritol tetrakismercaptoacetate andpentaerythritol tetrakismercaptopropionate.

(2) The polymerizable composition for an optical material according to(1), wherein the aliphatic polyisocyanate having 4 to 8 carbon atoms isone or more polyisocyanate selected from 1,6-hexamethylene diisocyanateand 1,5-pentamethylene diisocyanate.

(3) The polymerizable composition for an optical material according to(1) or (2), further including an active hydrogen compound containing twoor more active hydrogen groups in the molecule.

(4) In another embodiment, there is provided an optical materialobtained by curing the polymerizable composition for an optical materialaccording to any one of (1) to (3).

(5) In further another embodiment, there is provided a method forproducing an optical material, the method including the polymerizablecomposition for an optical material according to any one of (1) to (3).

(6) The method for producing an optical material according to (5),wherein the polymerizable composition for an optical material is moldedby cast polymerization.

According to the invention, a polymerizable composition for an opticalmaterial having a high refractive index, high heat resistance andfurther having satisfactory tinting property, and an optical materialobtainable from this polymerizable composition can be provided.

DETAILED DESCRIPTION

The invention will be now described herein with reference toillustrative embodiments. Those skilled in the art will recognize thatmany alternative embodiments can be accomplished using the teachings ofthe present invention and that the invention is not limited to theembodiments illustrated for explanatory purposed.

Hereinafter, embodiments of the invention will be described.

The polymerizable composition for an optical material of a oneembodiment contains tolylene diisocyanate, an aliphatic polyisocyanatehaving 4 to 8 carbon atoms and one or more polythiols selected frompentaerythritol tetrakismercaptoacetate and pentaerythritoltetrakismercaptopropionate.

As the tolylene diisocyanate according to the invention, 2,4-tolylenediisocyanate and 2,6-tolylene diisocyanate may be used individually oras a mixture. When a mixture of 2,4-tolylene diisocyanate and2,6-tolylene diisocyanate is used, the content of 2,4-tolylenediisocyanate is preferably 60% or more, and more preferably 75% or more.When a mixture is not used, 2,4-tolylene diisocyanate is preferred.Examples of commercially available tolylene diisocyanate includeCosmonate T-100 and Cosmonate T-80 manufactured by Mitsui Chemicals,Inc., or the like.

The aliphatic polyisocyanate having 4 to 8 carbon atoms according to theinvention is a linear or branched aliphatic polyisocyanate having 4 to 8carbon atoms, and is preferably a linear diisocyanate. Specific examplesof the aliphatic polyisocyanate having 4 to 8 carbon atoms includetetramethylene diisocyanate, pentamethylene diisocyanate, hexamethylenediisocyanate, pentamethylene diisocyanate, and octamethylenediisocyanate. From the viewpoint of availability, handlability, and heatresistance of the obtained resin, 1,6-hexamethylene diisocyanate and1,5-pentamethylene diisocyanate are preferred.

In addition to the tolylene diisocyanate and aliphatic polyisocyanatehaving 4 to 8 carbon atoms, another isocyanate compound can be used(hereinafter, the isocyanate compound other than tolylene diisocyanateand the aliphatic polyisocyanate having 4 to 8 carbon atoms will bereferred to as “other isocyanate compound”). Examples of the otherisocyanate compound include:

aliphatic polyisocyanate compounds such as 2,2,4-trimethylhexamethylenediisocyanate, 2,4,4-trimethylhexamethylene diisocyanate, lysinediisocyanatomethyl ester, and lysine triisocyanate;

alicyclic polyisocyanate compounds such as isophorone diisocyanate,bis(isocyanatomethyl)cyclohexane, dicyclohexylmethane diisocyanate,dicyclohexyldimethylmethane isocyanate,2,5-bis(isocyanatomethyl)-bicyclo[2.2.1]-heptane,2,6-bis(isocyanatomethyl)-bicyclo[2.2.1]-heptane,3,8-bis(isocyanatomethyl)tricyclodecane,3,9-bis(isocyanatomethyl)tricyclodecane,4,8-bis(isocyanatomethyl)tricyclodecane, and4,9-bis(isocyanatomethyl)tricyclodecane (additionally,2,5-bis(isocyanatomethyl)-bicyclo[2.2.1]-heptane and2,6-bis(isocyanatomethyl)-bicyclo[2.2.1]-heptane can be produced by theproduction methods described in WO 2008/001490, Japanese UnexaminedPatent Publication No. H03-095151 (1991-095151), Japanese UnexaminedPatent Publication No. 2003-055327, Japanese Unexamined PatentPublication No. 2003-055328, Japanese Unexamined Patent Publication No.H03-081255 (1991-081255), Japanese Unexamined Patent Publication No.H03-109361 (1991-109361), Japanese Unexamined Patent Publication No.H03-181446 (1991-181446), Japanese Unexamined Patent Publication No.2001-089424, and Japanese Unexamined Patent Publication No. H07-309827(1995-309827), and the compounds may be used individually or may be usedas a mixture. When the compounds are used as a mixture, the mixing ratiomay be optional);

aromatic polyisocyanate compounds such as 4,4′-diphenylmethanediisocyanate, diphenyl sulfide-4,4-diisocyanate, and phenylenediisocyanate;

heterocyclic polyisocyanate compounds such as2,5-diisocyanateothiophene, 2,5-bis(isocyanatomethyl)thiophene,2,5-diisocyanatotetrahydrothiophene,2,5-bis(isocyanatomethyl)tetrahydrothiophene,3,4-bis(isocyanatomethyl)tetrahydrothiophene,2,5-diisocyanato-1,4-dithiane, 2,5-bis(isocyanatomethyl)-1,4-dithiane,4,5-diisocyanato-1,3-dithiolane, and4,5-bis(isocyanatomethyl)-1,3-dithiolane;

or the like, but the examples are not limited to these exemplarycompounds.

Furthermore, in addition to tolylene diisocyanate and the aliphaticpolyisocyanate having 4 to 8 carbon atoms, compounds obtained bysubstituting some of the isocyanate groups of the above-mentionedisocyanate compound with isothiocyanate groups, can also be used.

Examples of such isothiocyanate compounds include aliphaticpolyisothiocyanate compounds such as hexamethylene diisothiocyanate,lysine diisothiocyanatomethyl ester, lysine triisothiocyanate,m-xylylene diisothiocyanate, bis(isothiocyanatomethyl) sulfide,bis(isothiocyanatoethyl) sulfide, and bis(isothiocyanatoethyl)disulfide;

alicyclic polyisothiocyanate compounds such as isophoronediisothiocyanate, bis(isothiocyanatomethyl)cyclohexane,dicyclohexylmethane diisothiocyanate, cyclohexane diisothiocyanate,methylcyclohexane diisothiocyanate,2,5-bis(isothiocyanatomethyl)-bicyclo[2.2.1]-heptane,2,6-bis(isothiocyanatomethyl)-bicyclo[2.2.1]-heptane,3,8-bis(isothiocyanatomethyl)tricyclodecane,3,9-bis(isothiocyanatomethyl)tricyclodecane,4,8-bis(isothiocyanatomethyl)tricyclodecane, and4,9-bis(isothiocyanatomethyl)tricyclodecane;

aromatic polyisothiocyanate compounds such as tolylene diisothiocyanate,4,4-diphenylmethane diisothiocyanate, and diphenyldisulfide-4,4-diisothiocyanate;

sulfur-containing heterocyclic polyisothiocyanate compounds such as2,5-diisothiocyanatothiophene, 2,5-bis(isothiocyanatomethyl)thiophene,2,5-isothiocyanatotetrahydrothiophene,2,5-bis(isothiocyanatomethyl)tetrahydrothiophene,3,4-bis(isothiocyanatomethyl)tetrahydrothiophene,2,5-diisothiocyanato-1,4-dithiane,2,5-bis(isothiocyanatomethyl)-1,4-dithiane,4,5-diisothiocyanato-1,3-dithiolane, and 4,5-bis(isothiocyanatomethyl)-1,3-dithiolane;

or the like, but the examples are not limited to these exemplarycompounds.

Furthermore, halogen-substituted forms such as chlorine-substitutedforms and bromine-substituted forms; alkyl-substituted forms;alkoxy-substituted forms; and nitro-substituted forms of theseisocyanate compounds, or prepolymer type modification products withpolyhydric alcohols, carbodiimide modification products, ureamodification products, biuret modification products, or dimerizedreaction products or the like can also be used as the other isocyanatecompound. These isocyanate compounds can be used individually or asmixtures of two or more kinds.

The ratio of composition by weight of tolylene diisocyanate (A) and thealiphatic polyisocyanate having 4 to 8 carbon atoms (B) is notparticularly limited. However, the ratio of composition by weight of A/Bis preferably 58 to 98/42 to 2, more preferably 58 to 90/42 to 10, evenpreferably 58 to 90/42 to 15. In this range, well-balanced opticalmaterial having heat resistance and tinting property can be obtained.

According to the invention, an active hydrogen compound may be furtheradded. The active hydrogen compound used in the invention is a compoundhaving at least two or more active hydrogen groups. Examples of theactive hydrogen group include a hydroxyl group and a mercapto group. Theactive hydrogen compound is preferably an aliphatic or aromatic activehydrogen compound having 1 to 12 carbon atoms, more preferably analiphatic or aromatic active hydrogen compound having 1 to 8 carbonatoms, and even more preferably an aliphatic active hydrogen compoundhaving 1 to 8 carbon atoms. The active hydrogen compound may contain anether bond, an ester bond, a sulfide bond or a disulfide bond in themolecule.

Specific examples include compounds containing a mercapto group and ahydroxyl group, such as 2-mercaptoethanol, 3-mercaptopropanol,4-mercaptobutanol, 5-mercaptopentanol, 6-mercaptohexanol,7-mercaptoheptanol, 8-mercaptooctanol, 3-mercapto-1,2-propanediol,glycerin bis(mercaptoacetate), 4-mercaptophenol, and2,3-dimercapto-1-propanol; compounds containing hydroxyl groups, such asethylene glycol, diethylene glycol, triethylene glycol, 1, 3-propyleneglycol, dipropylene glycol, 1,4-butanediol, 1,3-butanediol,1,5-pentanediol, 1,4-pentanediol, 1,3-pentanediol, 1,6-hexanediol,1,5-hexanediol, 1,4-hexanediol, 1,3-hexanediol, 1,2-cyclohexanediol,1,3-cyclohexanediol, 1,4-cyclohexanediol, 1,7-heptanediol,1,8-octanediol, trimethylolethane, trimethylolpropane, pentaerythritol,sorbitol, xylytol, 1,2-dihydroxybenzene, 1,3-dihydroxybenzene, 1,4-dihydroxybenzene, m-xylene glycol, p-xylene glycol, and o-xyleneglycol; and

compounds containing mercapto groups, such as methanedithiol,1,2-ethanedithiol, 1,2,3-propanetrithiol, 1,2-cyclohexanedithiol,bis(2-mercaptoethyl) ether, tetrakis(mercaptomethyl)methane, diethyleneglycol bis(2-mercaptoacetate), diethylene glycol bis(3-mercaptopropionate), ethylene glycol bis(2-mercaptoacetate), ethyleneglycol bis(3-mecaptopropionate), bis(mercaptomethyl) sulfide,bis(mercaptomethyl) disulfide, bis(mercaptomethyl) disulfide,bis(mercaptopropyl) sulfide, bis(mercaptomethylthio)methane,bis(2-mercaptoethylthio)methane, bis(3-mercaptopropylthio)methane,1,2-bis(mercaptomethylthio)ethane, 1,2-bis(2-mercaptoethylthio)ethane,1,2-bis(3-mercaptopropylthio)ethane, 1,2-dimercaptobenzene,1,3-dimercaptobenzene, 1,4-dimercaptobenzene,1,2-bis(mercaptomethyl)benzene, 1,3-bis(mercaptomethyl)benzene,1,4-bis(mercaptomethyl)benzene, 1,2-bis(mercaptoethyl)benzene,1,3-bis(mercaptoethyl)benzene, and 1,4-bis(mercaptoethyl)benzene.

From the viewpoint of high refractive index and high heat resistance aswell as high tinting property of the obtained resin, ethylene glycol,diethylene glycol, triethylene glycol, trimethylolpropane,2-mercaptoethanol, 3-mercaptopropanol, 1,2-ethanedithiol,1,3-bis(mercaptomethyl)benzene or the like are preferred, and ethyleneglycol, diethylene glycol, triethylene glycol, trimethylolpropane, and2-mercaptoethanol are more preferred.

These active hydrogen compounds may be used individually, or as mixturesof two or more kinds. These active hydrogen compounds may be in anoligomer form.

Furthermore, in addition to pentaerythritol tetrakismercaptoacetate andpentaerythritol tetrakismercaptopropionate, another polythiol compoundcan also be used (hereinafter, the polythiol compound other thanpentaerythritol tetrakismercaptoacetate and pentaerythritoltetrakismercaptopropionate is referred to as “other polythiolcompound”). Examples of the other polythiol compound include aliphaticpolythiol compounds such as trimethylolpropanetris(2-mercaptoacetate),trimethylolpropanetris(3-mercaptopropionate),trimethylolethanetris(2-mercaptoacetate),trimethylolethanetris(3-mercaptopropionate),1,2,3-tris(mercaptomethylthio)propane,1,2,3-tris(2-mercaptoethylthio)propane,1,2,3-tris(3-mercaptopropylthio)propane,tetrakis(mercaptomethylthiomethyl)methane,tetrakis(2-mercaptoethylthiomethyl)methane,tetrakis(3-mercaptopropylthiomethyl)methane, bis(2,3-dimercaptopropyl)sulfide, 2,5-dimercapto-1,4-dithiane,2,5-dimercaptomethyl-2,5-dimethyl-1,4-dithiane, and thioglycolic acidand mercaptopropionic acid esters, hydroxymethyl sulfidebis(2-mercaptoacetate), hydroxymethyl sulfide bis(3-mercaptopropionate),hydroxyethyl sulfide bis(2-mercaptoacetate), hydroxyethyl sulfidebis(3-mercaptopropionate), hydroxymethyl disulfidebis(2-mercaptoacetate), hydroxymethyl disulfidebis(3-mercaptopropionate), hydroxyethyl disulfidebis(2-mercaptoacetate), hydroxyethyl disulfidebis(3-mercaptopropionate), 2-mercaptoethyl ether bis(2-mercaptoacetate),2-mercaptoethyl ether bis(3-mercaptopropionate), thiodiglycolic acid bis(2-mercaptoethyl ester), thiodipropionic acid bis(2-mercaptoethylester), dithiodiglycolic acid bis(2-mercaptoethyl ester),dithiodipropionic acid bis(2-mercaptoethyl ester),1,1,3,3-tetrakis(mercaptomethylthio)propane,1,1,2,2-tetrakis(mercaptomethylthio)ethane,4,6-bis(mercaptomethylthio)-1,3-dithiacyclohexane,tris(mercaptomethylthio)methane, and tris(mercaptoethylthio)methane;

aromatic polythiol compounds such as 1,3,5-trimercaptobenzene1,3,5-tris(mercaptomethyl)benzene,1,3,5-tris(mercaptomethyleneoxy)benzene,1,3,5-tris(mercaptoethyleneoxy)benzene, 2,5-toluenedithiol,3,4-toluenedithiol, 1,5-naphthalenedithiol, 2,6-naphthalenedithiol,2-methylamino-4,6-dithiol-sym-triazine, 3,4-thiophene dithiol,bismuthiol, 4,6-bis(mercaptomethylthio)-1,3-dithiane, and2-(2,2,-bis(mercaptomethylthio)ethyl)-1,3-dithiethane;

heterocyclic polythiol compounds such as2-methylamino-4,6-dithiol-sym-triazine, 3,4-thiophenedithiol,bismuthiol, 4,6-bis(mercaptomethylthio)-1,3-dithiane, and2-(2,2-bis(mercaptomethylthio)ethyl)-1,3-dithiethane;or the like.However, the examples are not limited to these exemplary compounds.

Furthermore, oligomers or halogen-substituted forms such aschlorine-substituted forms or bromine-substituted forms ofpentaerythritol tetrakismercaptoacetate, pentaerythritoltetrakismercaptopropionate, active hydrogen compounds, and otherpolythiol compounds may be added to the polymerizable composition for anoptical material of the invention. These compounds can be usedindividually or as mixtures of two or more kinds.

Furthermore, the tolylene diisocyanate and aliphatic polyisocyanatehaving 4 to 8 carbon atoms used in the one embodiment, and the otherisocyanate compounds that are added as necessary (hereinafter, referredto as “isocyanate compounds) may be products obtained by preliminarilyreacting polythiol with a part of the active hydrogen compounds or theother polythiol compounds. Also, the polythiols used in the inventionmay be products obtained by preliminarily reacting the polythiols with apart of isocyanate compounds.

Examples of an epoxy compound that can be added as a resin modifyingagent include:

a phenolic epoxy compound obtainable by a condensation reaction of apolyhydric phenol compound and an epihalohydrin compound, such asbisphenol A glycidyl ether;

an alcohol-based epoxy compound obtainable by condensation of apolyhydric alcohol compound and an epihalohydrin compound, such ashydrogenated bisphenol A glycidyl ether;

a glycidyl ester-based epoxy compound obtainable by condensation of apolyvalent organic acid and an epihalohydrin compound, such as3,4-epoxycyclohexylmethyl-3′,4′-epoxycyclohexanecarboxylate;

an amine-based epoxy compound obtainable by condensation of a primary orsecondary diamine and an epihalohydrin compound;

an aliphatic polyvalent epoxy compound such as vinylcyclohexenediepoxide; or the like. However, the examples are not limited to theseexemplary compounds.

Examples of an episulfide compound that can be added as a resinmodifying agent include:

chain-like aliphatic 2,3-epithiopropylthio compounds such asbis(2,3-epithiopropylthio)sulfide, bis(2,3-epithiopropylthio)disulfide,bis(2,3-epithiopropylthio)methane, 1,2-bis(2,3-epithiopropylthio)ethane,and 1,5-bis(2,3-epithiopropylthio)-3-thiaphene;

2, 3-epithiopropylthio compounds having alicyclic heterocyclic rings,such as 1,3-bis(2,3-epithiopropylthio)cyclohexane, and2,5-bis(2,3-epithiopropylthiomethyl)-1,4-dithiane;

aromatic 2,3-epithiopropylthio compounds such as1,3-bis(2,3-epithiopropylthio)benzene and1,4-bis(2,3-epithiopropylthio)benzene; or the like. However the examplesare not limited to these exemplary compounds.

Examples of an organic acid and an anhydride thereof that can be addedas resin modifying agents include:

thiodiglycolic acid, thiodipropionic acid, dithiodipropionic acid,phthalic anhydride, hexahydrophthalic anhydride, methylhexahydrophthalicanhydride, methyltetrahydrophthalic anhydride, maleic anhydride,trimellitic anhydride, pyromellitic anhydride or the like, but theexamples are not limited to these exemplary compounds.

Examples of an olefin compound that can be added as a resin modifyingagent include:

(meth)acrylate compounds such as benzyl acrylate, benzyl methacrylate,cyclohexyl acrylate, cyclohexyl methacrylate, 2-hydroxyethyl acrylate,2-hydroxymethyl methacrylate, glycidyl acrylate, glycidyl methacrylate,phenoxyethyl acrylate, phenoxyethyl methacrylate, phenyl methacrylate,ethylene glycol diacrylate, ethylene glycol dimethacrylate, diethyleneglycol diacrylate, diethylene glycol dimethacrylate, triethylene glycoldiacrylate, triethylene glycol dimethacrylate, neopentyl glycoldiacrylate, neopentyl glycol dimethacrylate, ethylene glycol bisglycidylacrylate, ethylene glycol bisglycidyl methacrylate, bisphenol Adiacrylate, bisphenol A dimethacrylate, bisphenol F diacrylate,bisphenol F dimethacrylate, trimethylolpropane triacrylate,trimethylolpropane trimethacrylate, glycerol diacrylate, glyceroldimethacrylate, pentaerythritol triacrylate, pentaerythritoltetraacrylate, pentaerythritol tetramethacrylate, xylylene dithioldiacrylate, xylylene dithiol dimetahcrylate, mercaptoethyl sulfidediacrylate, and mercaptoethyl sulfide dimetahcrylate;

allyl compounds such as allyl glycidyl ether, diallyl phthalate, diallylterephthalate, diallyl isophthalate, and diethylene glycol bisallylcarbonate;

vinyl compounds such as styrene, chlorostyrene, methylstyrene,bromostyrene, dibromostyrene, divinylbenzene, and3,9-divinylspirobi(m-dioxane); or the like, but the examples are notlimited to these exemplary compounds.

These resin modifying agents can be used individually or as mixtures oftwo or more kinds.

The use ratio of the isocyanate compounds and the active hydrogencompound used in the invention is usually such that the molar ratio ofthe functional groups (NCO+NCS)/(SH+OH) is usually in the range of 0.8to 1.5, preferably in the range of 0.8 to 1.2, more preferably in therange of 0.8 to 1.1, and even more preferably in the range of 0.85 to1.05, based on the polymerizable composition for an optical material.

The invention also provides an optical material obtained by curing thepolymerizable composition for an optical material described above.

Here, the refractive index of the optical material can be regulated bythe type and composition ratios of the isocyanate compounds and activehydrogen compounds in the polymerizable composition, as desired.Particularly, it is demanded that the optical material of the oneembodiment has a high refractive index, and from this point of view, itis preferable to use, for example, a combination and composition ratioof isocyanate compounds and active hydrogen compounds that are capableof obtaining a resin having a refractive index of usually 1.55 orgreater, and preferably 1.59 or greater, as a refractive index measuredat e-line.

The optical material of the invention is also excellent in lightresistance. Here, light resistance can be evaluated based on themeasurement value of changes (hereinafter, referred to as “ΔYI”) in theyellow index (hereinafter, referred to as “YI”) after light irradiationfor 48 hours, as measured by a QUV tester. It is preferable that the ΔYIvalue of an optical material is as small as possible, from the viewpointof having excellent light resistance, but the ΔYI is usually 10.0 orless, preferably 7.0 or less, and more preferably 6.0 or less. The lowerlimit is not particularly limited, but for example, the lower limit isadjusted to 0.1 or greater.

The heat resistance of, the optical material of the invention ispreferably 90 degrees C. or higher, more preferably 95 degrees C. orhigher, and even more preferably 100 degrees C. or higher.

The optical material of the invention is excellent in tinting property.The tinting property as used in the invention means the ease of beingtinted when the optical material is tinted by immersing in a tintingdispersion liquid which has been prepared by adding a tinting agent inpurified water. Specifically, being excellent in tinting property meansthat when a tinted lens piece is scanned with a UV spectrophotometer(UV-1600 manufactured by Shimadzu Corp.) in the wavelength range of 400nm to 800 nm, the transmittance (% T) value at the maximum absorptionwavelength, 565 nm, is small.

Here, the tinting property of the optical material of the invention is,as expressed as the transmittance (% T) value that will be describedlater, preferably 60% T or less, more preferably 50% T or less, and evenmore preferably 45% T or less.

From another point of view, the invention provides a method forproducing an optical material by curing the polymerizable composition,for example, a method for producing an optical material by molding thepolymerizable composition by cast polymerization using a mold for lenscasting.

In order to mold by curing the mixture of isocyanate compounds andactive hydrogen compounds, which is the polymerizable composition for anoptical material, the polymerization catalyst described in WO2010/001550, a catalyst such as dialkyltin dichloride (specifically,dialkyltin dichloride having an alkyl group having 1 to 4 carbon atoms,for example, dimethyltin dichloride, dibutyltin dichloride)(hereinafter, also referred to as “curing catalyst”), and an ultravioletabsorber such as a benzotriazole compound, an internal releasing agentsuch as acidic phosphoric acid ester, a photostabilizer, an antioxidant,a reaction initiator such as a radical reaction initiator, a chainextending agent, a crosslinking agent, a coloring preventing agent, anoil-soluble tinting agent, and a filler may also be added using the sametechniques as those used in known molding methods as necessary.

When a feed solution is prepared by mixing the isocyanate compounds andactive hydrogen compounds with a reaction catalyst, a mold releasingagent or other additives, the addition of the catalyst, releasing agentor other additives is dependent on the solubility of the isocyanatecompounds and the active hydrogen compounds, but the catalyst, releasingagent or other additives may be added and dissolved in the isocyanatecompounds in advance, may be added and dissolved in the active hydrogencompounds, or may be added and dissolved in a mixture of the isocyanatecompounds and active hydrogen compounds. Alternatively, a mastersolution may be prepared by dissolving the materials in a portion of theisocyanate compounds or active hydrogen compounds prepared for use, andthen this master solution may be added to the composition. The order ofaddition is not limited to these exemplary methods, and is appropriatelyselected on the basis of operability, safety, convenience or the like.

Mixing is usually carried out at a temperature of 30 degrees C. orlower. From the viewpoint of the pot life of the mixture, it may bepreferable to carry out the mixing at a lower temperature. Furthermore,when an additive such as a catalyst or a releasing agent does notexhibit good solubility in the isocyanate compounds and active hydrogencompounds, the additive may be warmed in advance and then dissolved inthe isocyanate compounds, active hydrogen compounds or a mixturethereof.

Furthermore, depending on the properties demanded from obtainableplastic lenses, it is often preferable to carry out a defoamingtreatment under reduced pressure, a filtration treatment under pressureor under reduced pressure, or the like according to necessity.

Subsequently, a mold for lens casting in which the mixture of isocyanatecompounds and the active hydrogen compounds has been fed and apolarizing film is fixed, is heated in an oven or in an apparatuscapable of heating in water, over several hours to several ten hoursunder a predetermined temperature program, to perform molding by curing.

The temperature for polymerization curing cannot be defined because theconditions may vary with the composition of the mixture, type of thecatalyst, shape of the mold or the like, but the polymerization curingis carried out at a temperature of approximately −50 degrees C. to 200degrees C. for 1 hour to 100 hours.

Typically, it is general to initiate the polymerization curing attemperature in the range of 5 degrees C. to 40 degrees C., followed byslowly raising the temperature to the range of 80 degrees C. to 130degrees C., and to keep heating at the temperature for 1 hour to 4hours.

After completion of the polymerization curing, the product is removedfrom the mold for lens casting, and thus a plastic lens is obtained.

The plastic lens that is obtained from the optical material of the oneembodiment is preferably subjected to an annealing treatment by heatingthe lens released from the mold, for the purpose of alleviating thestrain due to polymerization. The annealing temperature is usually inthe range of 80 degrees C. to 150 degrees C., preferably in the range of100 degrees C. to 130 degrees C., and more preferably in the range of110 degrees C. to 130 degrees C. The annealing time is usually in therange of 0.5 hours to 5 hours, and preferably in the range of 1 hour to4 hours.

The plastic lens that is obtained from the optical material of the oneembodiment is used after a coating layer is provided on one surface oron both surfaces as necessary. Examples of the coating layer include aprimer layer, a hard coating layer, an anti-reflective coating layer, ananti-fog coating layer, an anti-fouling layer, a water-repellent layer,or the like. These coating layers may be used individually, or aplurality of coating layers may be integrated into a multilayer andused. In the case of providing coating layers on both surfaces,identical coating layers may be provided on the respective surfaces, ordifferent coating layers may be provided.

In these coating layers, an ultraviolet absorber for the purpose ofprotecting the lens or the eye from ultraviolet rays; an infraredabsorber for the purpose of protecting the eye from infrared rays; aphotostabilizer or an antioxidant for the purpose of enhancing weatherresistance of the lens; a tinting agent or a pigment, more specifically,a photochromic tinting agent or a photochromic pigment, for the purposeof increasing the stylishness of the lens; an antistatic agent; andother known additives for the purpose of enhancing the performance ofthe lens, also be used in combination. Various leveling agents may alsobe used for the purpose of improving coatability.

The primer layer is generally formed between the lens base material (theoptical material obtainable from the polymerizable composition of theone embodiment) and a hard coating layer, for the purpose of enhancingthe adhesiveness of the hard coating layer or the impact resistance ofthe plastic lens, and the layer thickness is usually about 0.1 μm to 10μm.

The primer layer is formed by, for example, a coating method or a drymethod. In the coating method, the primer layer is formed by applying aprimer composition by a known coating method such as spin coating or dipcoating, and solidifying the composition. In the dry method, the primerlayer is formed by a known dry method such as a CVD method or a vacuumdeposition method. Upon forming the primer layer, the surface of thelens may be subjected to a pretreatment such as alkali treatment, plasmatreatment or ultraviolet radiation treatment as necessary, for thepurpose of enhancing adhesiveness.

In regard to the primer composition, a material having high adhesivenessto the lens base material (the optical material obtainable from thepolymerizable composition of the one embodiment) when solidified into aprimer layer is preferable, and usually, a primer composition containinga urethane resin, an epoxy resin, a polyester resin, a melamine resin,or polyvinyl acetal as a main component, or the like is used. The primercomposition can be used without solvent, but an appropriate solvent thatdoes not affect the lens may be used for the purpose of adjusting theviscosity of the composition.

The hard coating layer is a coating layer intended to impart functionssuch as scratch resistance, abrasion resistance, moisture resistance,warm water resistance, heat resistance and weather resistance to thelens surface, and the layer thickness is usually about 0.3 μm to 30 μm.

The hard coating layer is formed by applying a hard coat composition bya known coating method such as spin coating or dip coating, and thencuring the composition. Examples of the curing method include heatcuring, curing by irradiation with an energy ray such as ultravioletrays or visible rays, and so on. Upon forming the hard coating layer,the surface to be coated (lens base material or primer layer) may besubjected to pretreatment such as alkali treatment, plasma treatment orultraviolet radiation treatment as necessary, for the purpose ofenhancing adhesiveness.

As the hard coat composition, generally mixtures of curableorganosilicon compounds and oxide microparticles of Si, Al, Sn, Sb, Ta,Ce, La, Fe, Zn, W, Zr, In and Ti (including composite oxidemicroparticles) are often used. In addition to these, amines, aminoacids, metal acetylacetonate complexes, organic acid metal salts,perchloric acids, salts of perchloric acids, acids, metal chlorides,polyfunctional epoxy compounds or the like may also be used. The hardcoat composition may be used without solvent, but an appropriate solventthat does not affect the lens may also be used.

The anti-reflective layer is usually formed on the hard coating layer,if necessary. The anti-reflective layer may be an inorganic layer or anorganic layer, and an inorganic layer is often formed by a dry methodsuch as a vacuum deposition method, a sputtering method, an ion platingmethod, an ion beam assist method or a CVD method, generally using aninorganic oxide such as SiO₂ or TiO₂. An organic layer is often formedby a wet method, generally using a composition containing anorganosilicon compound and silica microparticles having an internalcavity.

The antireflection layer may be a single layer or a multilayer, but whenthe antireflection layer is used as a single layer, it is preferablethat the refractive index of the antireflection layer is lower than therefractive index of the hard coating layer, by at least 0.1 or more. Inorder to exhibit the antireflection function more effectively, it ispreferable to prepare the layer as a multilayer antireflection film, andin that case, typically, a low-refractive index film and ahigh-refractive index film are alternately laminated. In this case aswell, it is preferable that the difference in refractive indices betweenthe low-refractive index film and the high-refractive index film is 0.1or more. Examples of the high-refractive index film include films ofZnO, TiO₂, CeO₂, Sb₂O₅, SnO₂, ZrO₂, Ta₂O₅ or the like, and examples ofthe low-refractive index film include SiO₂ film or the like. The filmthickness is usually about 50 nm to 150 nm.

Furthermore, the plastic lens that is obtained from the optical materialof the one embodiment may be subjected to rear surface polishing, anantistatic treatment, a tinting treatment, a photochromic treatment orthe like, according to necessity.

Since such a plastic lens can be made thin, it is useful as a spectacleslens, and particularly as a vision corrective lens, and since theplastic lens has excellent, tinting property, it is rich in stylishness.

EXAMPLES

Hereinafter, the invention will be described in more detail withreference to Examples, but the invention is not limited to theseExamples.

A lens obtained by polymerization was evaluated by performing aperformance test. The performance test evaluated color, refractiveindex/Abbe number, heat resistance, specific gravity and tintingproperty, by the following testing methods.

Color: A flat resin plate having a thickness of 9 mm was produced, andthe yellow index (YI) was measured with a colorimeter (CR-200manufactured by Minolta Co., Ltd.).

Refractive index (ne) Abbe number (υe) : Measurement was made at 20degrees C. using a Pulfrich refractometer KPR-30 manufactured byShimadzu Corp.

Heat resistance: The glass transition temperature (Tg) measured by a TMApenetration method (load of 50 g, pincher 0.5 mmφ) using TMA-60manufactured by Shimadzu Corp. was designated as the heat resistance.

Specific gravity: Measurement was made by Archimedes' method at 20degrees C.

Tinting property: A tinting dispersion liquid was prepared by adding, astinting agents, 1.5 g of “MLP-Blue”, 2.0 g of “MLP-Yellow” and 1.5 g of“MLP-Red” , which are dispersion tints for spectacle lenses manufacturedby Mitsui Chemicals Inc. to 995 g of purified water. This dispersionliquid was heated to 90 degrees C., and then a plastic lens piece havinga thickness of 9 mm was tinted by immersing therein for 5 minutes at 90degrees C. The tinted lens piece was scanned over a wavelength range of400 nm to 800 nm using a UV spectrophotometer (UV-1600 manufactured byShimadzu Corp.), and the transmittance (% T) at the maximum absorptionwavelength, 565 nm, was measured.

Light resistance test: A flat resin plate having a thickness of 2 mm wasproduced and was irradiated for 48 hours using a QUV tester(manufactured by Q-Lab, Inc.), and then ΔYI was measured from the resincolor before and after the irradiation. (The QUV test was carried outunder conditions of a luminance of 0.35 W/m² and a black paneltemperature of 50 degrees C., using UVB-340 as a light source.)

Example 1

26.4 g of tolylene diisocyanate (Cosmonate T-80 (Lot No.: K09B26302)manufactured by Mitsui Chemicals, Inc.) and 13.7 g of hexamethylenediisocyanate were mixed and dissolved, and 0.01 g of dimethyltindichloride as a curing catalyst, 1.50 g of Biosorb 583 as an ultravioletabsorber, and 0.10 g of Zelec UN (acidic phosphoric acid ester:registered trademark, manufactured by Stepan Company) as an internalreleasing agent, were added thereto. The resulting mixture was mixed anddissolved at 20 degrees C. After dissolving the materials, 59.9 g ofpentaerythritol tetrakismercaptopropionate was added to the solution,and the mixture was mixed and dissolved to obtain a uniform solution.This uniform solution was defoamed at 600 Pa for 1 hour, and then wasfiltered through a 1-μm Teflon (registered trademark) filter. Thefiltered solution was fed into a mold formed from a glass mold andtapes. This mold was placed in an oven, and polymerization was carriedout by slowly increasing the temperature from 25 degrees C. to 120degrees C. approximately over 24 hours. After completion ofpolymerization, the mold was taken out from the oven, and the resin wasobtained by releasing from the mold. The obtained resin was annealed for4 hours at 120 degrees C. The obtained resin had a YI value of 7.9, arefractive index (ne) of 1.595, an Abbe number (υe) of 32, a heatresistance of 98 degrees C., a resin specific gravity of 1.34, and alight resistance (48 hours) ΔYI value of 6.6. The transmittance at 565nm of the obtained resin after tinting was 29% T.

Examples 2 to 8 and Comparative Examples 1 to 3

Polymerization was carried out with the monomer compositions shown inTable 1 under the same conditions as those used in Example 1 in terms ofthe types and amounts of addition of the curing catalyst, ultravioletabsorber and internal releasing agent, and the curing conditions. Theproperties of the obtained resin are summarized in Table 1.

Example 9

Polymerization was carried out with the monomer compositions shown inTable 1, under the same conditions as those used in Example 1 in termsof the type and amount of addition of the internal releasing agent, andthe curing conditions, except that 0.01 g of dibutyltin dichloride wasused as a curing catalyst. Cosmonate T-100 (Lot No.: K09B04505)manufactured by Mitsui Chemicals, Inc. was used as tolylenediisocyanate. The properties of the obtained resin are summarized inTable 1.

TABLE 1 Abbe Heat Tinting Monomer Color Refractive Number resistanceSpecific property Light resistance Composition (g) [YI] index [ne] [νe][degree C.] gravity [565 nm/% T] [48 HR]ΔYI Example A-1(26.4)/B-1(13.7)7.9 1.595 32 98 1.34 29 6.6 1 C-1(59.9) Example A-1(35.2)/B-1(18.3) 6.71.601 31 107 1.33 15 4.0 2 C-1(31.9)/D-1(14.6) ExampleA-1(34.1)/B-1(8.4) 6.0 1.598 31 97 1.34 24 9.8 3 C-1(53.6)/D-2(3.9)Example A-1(33.7)/B-1(8.1) 7.6 1.597 31 103 1.34 20 — 4C-1(52.8)/D-3(5.4) Example A-1(34.8)/B-1(8.4) 6.9 1.601 30 115 1.35 41 —5 C-1(54.5)/D-4(2.3) Example A-1(34.5)/B-1(8.3) 8.4 1.599 31 116 1.34 59— 6 C-1(53.8)/D-5(3.4) Example A-1(35.8)/B-2(17.1) 6.7 1.604 30 107 1.3423 — 7 C-1(32.3)/D-1(14.8) Example A-1(36.4)/B-1(18.9) 9.7 1.606 31 1161.36 42 — 8 C-2(29.6)/D-1(15.1) Comp. A-2(50.8) 5.6 1.598 39 113 1.31 670.8 Ex. 1 C-1(25.6)/C-3(23.9) Comp. A-3(43.6) 5.9 1.598 36 93 1.36 20 —Ex. 2 C-1(56.4) Comp. A-1(41.9)/B-1(10.1) 9.6 1.666 27 116 1.35 69 4.4Ex. 3 C-3(43.2)/D-1(4.8) Example A-1-1(35.2)/B-1(18.3) 5.6 1.602 30 1001.33 7 4.8 9 C-1(31.9)/D-1(14.6)

Examples 10 to 15

Polymerization was carried out with the monomer compositions shown inTable 2, under the same conditions as those used in Example 1 in termsof the types and amounts of addition of the curing catalyst, ultravioletabsorber and internal releasing agent, and the curing conditions. Theproperties of the obtained resins are summarized in Table 2.

TABLE 2 Abbe Heat Tinting Monomer Color Refractive Number resistanceSpecific property Light resistance Composition (g) [YI] Index [ne] [νe][degree C.] gravity [565 nm/% T] [48 HR]ΔYI Example A-1(34.4)/B-1(17.9)6.1 1.600 31 97 1.33 8 4.4 10 C-1(32.7)/D-1(15.0) ExampleA-1(33.6)/B-1(17.5) 6.1 1.600 31 90 1.33 4 5.4 11 C-1(33.5)/D-1(15.4)Example A-1(30.9)/B-1(16.1) 6.1 1.599 31 100 1.33 13 4.2 12C-1(44.0)/D-1(9.0) Example A-1(30.0)/B-1(15.6) 6.0 1.598 31 91 1.33 45.6 13 C-1(44.7)/D-1(9.7) Example A-1(34.1)/B-1(8.4) 8.0 1.600 30 1061.35 38 6.5 14 C-1(53.6)/D-2(3.9) Example A-1(33.3)/B-1(8.1) 7.3 1.59831 100 1.35 23 6.8 15 C-1(54.6)/D-2(4.0)

Example 16

The curing catalyst (polymerization catalyst) described in

Example A1 of WO 2010/001550 was used as a curing catalyst.Specifically, polymerization was carried out with the monomercomposition shown in Table 3 under the same conditions as those used inExample 1 in terms of the types and amounts of addition of theultraviolet absorber and internal releasing agent, and the curingconditions, except that 26.4 g of tolylene diisocyanate (Cosmonate T-80(Lot No.: K09B26302), manufactured by Mitsui Chemicals, Inc.) and 13.7 gof hexamethylene diisocyanate were mixed and dissolved, and 0.20 g of amixture of 0.17 g of a solution of tri-n-octylmethylammmonium chloridein isopropyl alcohol (containing 25% of isopropanol) (manufactured byLion Akzo Co. , Ltd.) and 0.03 g of methanesulfonic acid (manufacturedby Tokyo Chemical Industry Co., Ltd.), which had been thoroughly mixedin advance, and 0.02 g of zinc dibutyldithiocarbamate (manufactured byKawaguchi Chemical Industry Co., Ltd.) were added as a curing catalyst.The properties of the obtained resin are summarized in Table 3.

Examples 17 to 20

Polymerization was carried out with the monomer compositions shown inTable 3 under the same conditions as those used in Example 1 in terms ofthe types and amounts of addition of the ultraviolet absorber andinternal releasing agent, and the curing conditions, except that 0.01 gof dibutyltin dichloride was used as a curing catalyst. The propertiesof the obtained resins are summarized in Table 3.

TABLE 3 Abbe Heat Tinting Monomer Color Refractive Number resistanceSpecific property Light resistance Composition (g) [YI] index [ne] [νe][degree C.] gravity [565 nm/% T] [48 HR]ΔYI Example A-1(26.4)/B-1(13.7)7.1 1.596 32 96 1.34 24 6.1 16 C-1(59.9) ExampleA-1(34.5)/B-1(9.0)/A-2(11.0) 6.5 1.602 31 117 1.33 39 3.3 17C-1(31.2)/D-1(14.3) C-1(33.5)/D-1(15.4) Example A-1(34.4)/B-1(17.9) 6.11.601 31 98 1.33 10 4.3 18 C-1(32.7)/D-1(15.0) ExampleA-1(33.7)/B-1(17.5) 6.1 1.600 31 92 1.33 5 5.0 19 C-1(33.5)/D-1(15.3)Example A-1(36.1)/B-1(18.8) 7.5 1.602 30 114 1.33 27 3.1 20C-1(31.0)/D-1(14.1)

Example 21

20.0 g of tolylene diisocyanate (Cosmonate T-80 (Lot No.: K09B26302)manufactured by Mitsui Chemicals, Inc.) and 20.0 g of hexamethylenediisocyanate were mixed and dissolved, and 0.01 g of dimethyltindichloride as a curing catalyst, 1.50 g of Biosorb 583 as an ultravioletabsorber, and 0.10 g of Zelec UN (acidic phosphoric acid ester:registered trademark, manufactured by Stepan Company) as an internalreleasing agent, were added thereto. The resulting mixture was mixed anddissolved at 20 degrees C. After dissolving the materials, 60.0 g ofpentaerythritol tetrakismercaptopropionate was added to the solution,and the mixture was mixed and dissolved to obtain a uniform solution.This uniform solution was defoamed at 600 Pa for 1 hour, and then wasfiltered through a 1-μm Teflon (registered trademark) filter. Thefiltered solution was fed into a mold formed from a glass mold andtapes. This mold was placed in an oven, and polymerization was carriedout by slowly increasing the temperature from 25 degrees C. to 120degrees C. approximately over 24 hours. After completion ofpolymerization, the mold was taken out from the oven, and the resin wasobtained by releasing from the mold. The obtained resin was annealed for4 hours at 120 degrees C. The obtained resin had a YI value of 7.7, arefractive index (ne) of 1.587, an Abbe number (υe) of 34, a heatresistance of 91 degrees C., a resin specific gravity of 1.33, and alight resistance (48 hours) ΔYI value of 4.2. The transmittance at 565nm of the obtained resin after tinting was 17% T.

Example 22

24.1 g of tolylene diisocyanate (Cosmonate T-80 (Lot No.: K09B26302)manufactured by Mitsui Chemicals, Inc.) and 16.1 g of hexamethylenediisocyanate were mixed and dissolved, and 0.01 g of dimethyltindichloride as a curing catalyst, 1.50 g of Biosorb 583 as an ultravioletabsorber, and 0.10 g of Zelec UN (acidic phosphoric acid ester:registered trademark, manufactured by Stepan Company) as an internalreleasing agent, were added thereto. The resulting mixture was mixed anddissolved at 20 degrees C. After dissolving the materials, 59.8 g ofpentaerythritol tetrakismercaptopropionate was added to the solution,and the mixture was mixed and dissolved to obtain a uniform solution.This uniform solution was defoamed at 600 Pa for 1 hour, and then wasfiltered through a 1-μm Teflon (registered trademark) filter. Thefiltered solution was fed into a mold formed from a glass mold andtapes. This mold was placed in an oven, and polymerization was carriedout by slowly increasing the temperature from 25 degrees C. to 120degrees C. approximately over 24 hours. After completion ofpolymerization, the mold was taken out from the oven, and the resin wasobtained by releasing from the mold. The obtained resin was annealed for4 hours at 120 degrees

C. The obtained resin had a YI value of 7.9, a refractive index (ne) of1.593, an Abbe number (υe) of 32, a heat resistance of 98 degrees C., aresin specific gravity of 1.34, and a light resistance (48 hours) ΔYIvalue of 4.5. The transmittance at 565 nm of the obtained resin aftertinting was 22% T.

Example 23

28.2 g of tolylene diisocyanate (Cosmonate T-80 (Lot No.: K09B26302)manufactured by Mitsui Chemicals, Inc.) and 12.1 g of hexamethylenediisocyanate were mixed and dissolved, and 0.01 g of dimethyltindichloride as a curing catalyst, 1.50 g of Biosorb 583 as an ultravioletabsorber, and 0.10 g of Zelec UN (acidic phosphoric acid ester:registered trademark, manufactured by Stepan Company) as an internalreleasing agent, were added thereto. The resulting mixture was mixed anddissolved at 20 degrees C. After dissolving the materials, 59.7 g ofpentaerythritol tetrakismercaptopropionate was added to the solution,and the mixture was mixed and dissolved to obtain a uniform solution.This uniform solution was defoamed at 600 Pa for 1 hour, and then wasfiltered through a 1-μm Teflon (registered trademark) filter. Thefiltered solution was fed into a mold formed from a glass mold andtapes. This mold was placed in an oven, and polymerization was carriedout by slowly increasing the temperature from 25 degrees C. to 120degrees C. approximately over 24 hours. After completion ofpolymerization, the mold was taken out from the oven, and the resin wasobtained by releasing from the mold. The obtained resin was annealed for4 hours at 120 degrees C. The obtained resin had a YI value of 8.1, arefractive index (ne) of 1.598, an Abbe number (υe) of 31, a heatresistance of 104 degrees C., a resin specific gravity of 1.35, and alight resistance (48 hours) ΔYI value of 4.6. The transmittance at 565nm of the obtained resin after tinting was 36% T.

Example 24

51.1 g of tolylene diisocyanate (Cosmonate T-80 (Lot No.: K09B26302)manufactured by Mitsui Chemicals, Inc.) and 2.7 g of hexamethylenediisocyanate were mixed and dissolved, and 0.01 g of dimethyltindichloride as a curing catalyst, 1.50 g of Biosorb 583 as an ultravioletabsorber, and 0.10 g of Zelec UN (acidic phosphoric acid ester:registered trademark, manufactured by Stepan Company) as an internalreleasing agent, were added thereto. The resulting mixture was mixed anddissolved at 20 degrees C. After dissolving the materials, 31.7 g ofpentaerythritol tetrakismercaptopropionate and 14.5 g of2-mercaotethanol was added to the solution, and the mixture was mixedand dissolved to obtain a uniform solution. This uniform solution wasdefoamed at 600 Pa for 1 hour, and then was filtered through a 1-μmTeflon (registered trademark) filter. The filtered solution was fed intoa mold formed from a glass mold and tapes. This mold was placed in anoven, and polymerization was carried out by slowly increasing thetemperature from 25 degrees C. to 120 degrees C. approximately over 24hours. After completion of polymerization, the mold was taken out fromthe oven, and the resin was obtained by releasing from the mold. Theobtained resin was annealed for 4 hours at 120 degrees C. The obtainedresin had a YI value of 7.5, a refractive index (ne) of 1.620, an Abbenumber (υe) of 28, a heat resistance of 117 degrees C., a resin specificgravity of 1.35. The transmittance at 565 nm of the obtained resin aftertinting was 59% T.

Example 25

48.4 g of tolylene diisocyanate (Cosmonate T-80 (Lot No.: K09B26302)manufactured by Mitsui Chemicals, Inc.) and 5.4 g of hexamethylenediisocyanate were mixed and dissolved, and 0.01 g of dimethyltindichloride as a curing catalyst, 1.50 g of Biosorb 583 as an ultravioletabsorber, and 0.10 g of Zelec UN (acidic phosphoric acid ester:registered trademark, manufactured by Stepan Company) as an internalreleasing agent, were added thereto. The resulting mixture was mixed anddissolved at 20 degrees C. After dissolving the materials, 31.7 g ofpentaerythritol tetrakismercaptopropionate and 14.5 g of2-mercaotethanol was added to the solution, and the mixture was mixedand dissolved to obtain a uniform solution. This uniform solution wasdefoamed at 600 Pa for 1 hour, and then was filtered through a 1-μmTeflon (registered trademark) filter. The filtered solution was fed intoa mold formed from a glass mold and tapes. This mold was placed in anoven, and polymerization was carried out by slowly increasing thetemperature from 25 degrees C. to 120 degrees C. approximately over 24hours. After completion of polymerization, the mold was taken out fromthe oven, and the resin was obtained by releasing from the mold. Theobtained resin was annealed for 4 hours at 120 degrees C. The obtainedresin had a YI value of 7.1, a refractive index (ne) of 1.617, an Abbenumber (υe) of 28, a heat resistance of 111 degrees C., a resin specificgravity of 1.35. The transmittance at 565 nm of the obtained resin aftertinting was 45% T.

Example 26

45.7 g of tolylene diisocyanate (Cosmonate T-80 (Lot No.:

K09B26302) manufactured by Mitsui Chemicals, Inc.) and 8.1 g ofhexamethylene diisocyanate were mixed and dissolved, and 0.01 g ofdimethyltin dichloride as a curing catalyst, 1.50 g of Biosorb 583 as anultraviolet absorber, and 0.10 g of Zelec UN (acidic phosphoric acidester: registered trademark, manufactured by Stepan Company) as aninternal releasing agent, were added thereto. The resulting mixture wasmixed and dissolved at 20 degrees C. After dissolving the materials,31.7 g of pentaerythritol tetrakismercaptopropionate and 14.5 g of2-mercaotethanol was added to the solution, and the mixture was mixedand dissolved to obtain a uniform solution. This uniform solution wasdefoamed at 600 Pa for 1 hour, and then was filtered through a 1-μmTeflon (registered trademark) filter. The filtered solution was fed intoa mold formed from a glass mold and tapes. This mold was placed in anoven, and polymerization was carried out by slowly increasing thetemperature from 25 degrees C. to 120 degrees C. approximately over 24hours. After completion of polymerization, the mold was taken out fromthe oven, and the resin was obtained by releasing from the mold. Theobtained resin was annealed for 4 hours at 120 degrees C. The obtainedresin had a YI value of 6.9, a refractive index (ne) of 1.604, an Abbenumber (υe) of 29, a heat resistance of 109 degrees C., a resin specificgravity of 1.34. The transmittance at 565 nm of the obtained resin aftertinting was 41% T.

Example 27

32.1 g of tolylene diisocyanate (Cosmonate T-80 (Lot No.: K09B26302)manufactured by Mitsui Chemicals, Inc.) and 21.4 g of hexamethylenediisocyanate were mixed and dissolved, and 0.01 g of dimethyltindichloride as a curing catalyst, 1.50 g of Biosorb 583 as an ultravioletabsorber, and 0.10 g of Zelec UN (acidic phosphoric acid ester:registered trademark, manufactured by Stepan Company) as an internalreleasing agent, were added thereto. The resulting mixture was mixed anddissolved at 20 degrees C. After dissolving the materials, 31.9 g ofpentaerythritol tetrakismercaptopropionate and 14.6 g of2-mercaotethanol was added to the solution, and the mixture was mixedand dissolved to obtain a uniform solution. This uniform solution wasdefoamed at 600 Pa for 1 hour, and then was filtered through a 1-μmTeflon (registered trademark) filter. The filtered solution was fed intoa mold formed from a glass mold and tapes. This mold was placed in anoven, and polymerization was carried out by slowly increasing thetemperature from 25 degrees C. to 120 degrees C. approximately over 24hours. After completion of polymerization, the mold was taken out fromthe oven, and the resin was obtained by releasing from the mold. Theobtained resin was annealed for 4 hours at 120 degrees C. The obtainedresin had a YI value of 6.6, a refractive index (ne) of 1.597, an Abbenumber (υe) of 31, a heat resistance of 96 degrees C., a resin specificgravity of 1.32. The transmittance at 565 nm of the obtained resin aftertinting was 13% T.

The properties of the obtained resins in Example 21 to 27 are summarizedin Table 4.

TABLE 4 Abbe Heat Tinting Monomer Color Refractive Number resistanceSpecific property Light resistance the rario of Composition (g) [YI]index [ne] [νe] [degree C.] gravity [565 nm/% T] [48 HR] ΔYI A-1 to B-1Example A-1(20.0)/B-1(20.0) 7.7 1.587 34 91 1.33 17 4.2 A-1:B-1 = 50:5021 C-1(60.0) Example A-1(24.1)/B-1(16.1) 7.9 1.593 32 98 1.34 22 4.5A-1:B-1 22 C-1(59.8) 60:40 Example A-1(28.2)/B-1(12.1) 8.1 1.598 31 1041.35 36 4.6 A-1:B-1 23 C-1(59.7) 70:30 Example A-1(51.1)/B-1(2.7) 7.51.620 28 117 1.35 59 — A-1:B-1 24 C-1(31.7)/D-1(14.5) 95:5 ExampleA-1(48.4)/B-1(5.4) 7.1 1.617 28 111 1.35 45 — A-1:B-1 25C-1(31.7)/D-1(14.5) 90:10 Example A-1(45.7)/B-1(8.1) 6.9 1.604 29 1091.34 41 — A-1:B-1 26 C-1(31.7)/D-1(14.5) 85:15 ExampleA-1(32.1)/B-1(21.4) 6.6 1.597 31 96 1.32 13 — A-1:B-1 27C-1(31.9)/D-1(14.6) 60:40

The reference numbers used for the monomer compositions in the Tables 1to 4 represent the following.

A-1: Tolylene diisocyanate (Cosmonate T-80 (Lot No.: K09B26302)manufactured by Mitsui Chemicals, Inc.)

A-1-1: Tolylene diisocyanate (Cosmonate T-100 (Lot No.: K09B04505)manufactured by Mitsui Chemicals, Inc.)

A-2: Mixture of 2,5-bis(isocyanatomethyl)-bicyclo[2.2.1]heptane and2,6-bis(isocyanatomethyl)-bicyclo[2.2.1]heptane

A-3: m-xylene diisocyanate

B-1: 1,6-Hexamethylene diisocyanate

B-2: 1,5-Pentane diisocyanate

C-1: Pentaerythritol tetrakismercaptopropionate

C-2: Pentaerythritol tetrakismercaptoacetate

C-3: 4-Mercaptomethyl-1,8-dimercapto-3,6-dithiaoctane

D-1: 2-Mercaptoethanol

D-2: Diethylene glycol

D-3: Triethylene glycol

D-4: Ethylene glycol

D-5: Trimethylolpropane

From the results of Tables 1 to 4, it can be seen that the materials ofExample 1 to Example 27 are well-balanced materials which have highrefractive indices and high heat resistance and also have high tintingproperty.

On the other hand, the Comparative Example 1 has a high refractive indexand high heat resistance, but is inferior in the tinting performance ascompared to the materials of the invention. That is, the ComparativeExample 1 is excellent only in heat resistance, and has poor tintingproperty. More specifically, to compare with an example having a closeglass transition temperature which serves as an index of heatresistance, the Example 5 has a heat resistance higher than theComparative Example 1 by 2 degrees C., but both are excellent in heatresistance. However, the Example 5 has better tinting property than theComparative Example 1 by 26% T.

It is apparent that the present invention is not limited to the aboveembodiment, and may be modified and changed without departing from thescope and spirit of the invention.

1. A polymerizable composition for an optical material comprisingtolylene diisocyanate, an aliphatic polyisocyanate having 4 to 8 carbonatoms, one or more polythiols selected from pentaerythritoltetrakismercaptoacetate and pentaerythritol tetrakismercaptopropionateand an active hydrogen compound containing two or more active hydrogengroups in the molecule.
 2. The polymerizable composition for an opticalmaterial according to claim 1, wherein said aliphatic polyisocyanatehaving 4 to 8 carbon atoms is one or more polyisocyanates selected fromhexamethylene diisocyanate and pentamethylene diisocyanate.
 3. Anoptical material obtained by curing the polymerizable composition for anoptical material according to claim
 1. 4. The method for producing anoptical material, the method comprising curing the polymerizablecomposition for an optical material according to claim
 1. 5. The methodfor producing an optical material according to claim 4, wherein saidpolymerizable composition for an optical material is molded by castpolymerization.